This application incorporates by reference Taiwanese application Serial No. 089217702, Filed on Oct. 12, 2000.
1. Field of the Invention
The invention relates in general to a photo-sensing apparatus, and more particularly to an optical module, which can be calibrated at least in four directions.
2. Description of the Related Art
The advance of hi-technology recently is leading the revolution of electric equipment and appliance such as computers, computer peripherals, and multi-functional peripherals. For example, scanners are developed to have resolution up to 1200 dpi and 9600 dpi. Besides higher quality, cost down is also an important issue for the scanner manufactures to be competitive.
Most commercial scanners apply charge couple device (CCD) as a photo sensor to sense the light reflected from the to-be-scanned document. In order to obtain a better image, the path of the reflected light should be perpendicular to the surface of the optical module. Thus, the position of the CCD module should be adjustable precisely to increase the scanning quality.
FIG. 1A shows the ideal relative position of the CCD module and the path of the light. The ideal position of the CCD module and the path of the light are perpendicular to each other. Herein, the CCD module 100 is located parallel to YZ plane and the light is moving along the X axis.
The CCD module 100 is typically assembled with a carriage. The CCD module 100 and the carriage together form an optical module. The misalignment of the CCD module 100 during the assembling process is hard to avoid. Thus, adjusting the CCD module is an important step after assembly. The orientation of the CCD module 100 is generally designed to be able to move along the Z axis (as shown in FIG. 1B), to move along the Y axis (as shown in FIG. 1C), to rotate on the X axis (as shown in FIG. 1D), to rotate on the Z axis (as shown in FIG. 1E), and to move along the X axis (as shown in FIG. 1F).
Three-direction and five-direction adjustable optical modules are two conventional designs. The CCD module of the conventional three-direction adjustable optical module can be manually adjusted to have the movements like moving along the Z and Y axes and rotates on the X axis. The optical module of the conventional three-direction adjustable optical module can be further adjusted by focusing the lens along the X axis.
The CCD module of the five-direction adjustable optical module, with the aid of extra devices, has the movements like moving along the X, Y, and Z axes and rotating on the X and Z axes.
The conventional three-direction adjustable optical module 200 is illustrated in FIG. 2, which includes a carriage 210 with a coupling window 210a, and a CCD module 220. The coupling window 210a has a screw hole 240. The CCD module 220 and the carriage 210 can be connected by using screws 230 to penetrate the CCD module 220 and fix in the screw hole 240 of the coupling window 210a. 
The conventional three-direction adjustable optical module 200 has the advantage of low cost since three-direction adjustment can be easily obtained by simple design. For the purpose of further cost down, the carriage 210 is typically made of plastics. However, the process of plastic formation tends to cause flaw on the carriage 210. If the coupling window 210a is made not parallel to the YZ plane, the CCD module 220 fixed thereon can not be parallel to the YZ plane, neither. Since the conventional three-direction adjustable optical module 200 is not able to rotate on the XZ axis, the CCD module 220 can not be calibrated. It is therefore apparent that the image quality will be greatly effected.
A five-direction adjustable optical module, as shown in FIG. 3, was then proposed. The conventional five-direction adjustable optical module is able to move along the X, Y, and Z axes and rotate on the X and Z axes. As shown in FIG. 3, the conventional five-direction adjustable optical module 300 includes a carriage 310, CCD module 320, device 330, device 340 and device 350. The CCD module 320 is indirectly connected to the contact window 310a of the carriage 310 and there are the device 330, device 340, and device 350 sequentially between the carriage 310 and the CCD module 320. The CCD module 320 is calibrated by the combination of the device 330, device 340, and device 350 under the control of a calibration program rather than manual control. However, it is apparent that the five-direction adjustable optical module 300 needs more devices and is more complicated so that the cost thereof is rather high and is therefore less competitive in the market.
To sum up, the conventional optical module has the following disadvantages:
1. the CCD module of the conventional three-direction adjustable optical module can not rotate on the Z axis; thus, the calibration result can not be optimized; and
2. the conventional five-direction adjustable optical module is less competitive in the market, regarding the cost and price.
It is therefore an object of the invention to provide a four-direction adjustable optical module, which is based on a three-direction adjustable optical module and is further modified to rotate on the Z-axis. Hence, the four-direction adjustable optical module of the invention is simple in structure but can be calibrated in at least four directions.
According to the object of the invention, a four-direction adjustable optical module including a carriage and a CCD module is disclosed. The carriage includes a coupling window for coupling with the CCD module. Each of the two sides of the CCD module includes a screw hole and an elastic device. The elastic device slightly protrudes from the surface of the coupling window. While the CCD module and the coupling window are coupled, screws are employed to screw through the CCD module and into the screw holes of the coupling windows. Therefore, the elastic devices deform by the stress from the CCD module. By adjusting the tightness of the screws, the orientation of the CCD module rotating on the Z axis can be calibrated. Thus, the adjustable optical module of the invention can be calibrated at least in four directions.